Deep-hardened alloy steel having improved impact strength



1960 N. J. CULP 2,950,968

DEEP-HARDENED ALLOY STEEL HAVING IMPROVED I MPACT STRENGTH Filed May 51,1957 2 Sheets-Sheet 2 I I I I I 0 IO 20 3O 4O 5O 6O 7O 8O 90 I00 0 A CuOF TOTAL MN+Cu CONTENT RELATION OF IMPACT STRENGTH TO COPPER ADDITIONSAS A FUNCTION OF MANGANESE PLUS COPPER CONTENT Aug. 30, 1960 N. J. CULP2,950,968

DEEP-HARDENED ALLOY STEEL HAVING IMPROVED IMPACT STRENGTH Filed May 51,1957 2 Sheets-Sheet Z 8 0.50 m 1 U V 0.40

I I I I I 0 IO 20 3O 40 5O 6O 7O 8O 90 I00 0 A Cu OF TOTAL MN-I-CUCONTENT RELATION 0F IMPACT STRENGTH TO COPPER ADDITIONS AS A FUNCTION OFMANGANESE PLUS COPPER CONTENT DEEP-HARDENED ALLOY STEEL HAVING EWRGVEDIMPACT STRENGTH Neil .l. Culp, West Lawn, Pan, assignor to The CarpenterSteel Company, Reading, Pa., a corporation of New Jersey Filed May 31,1957, Ser. No. 662,805

8 Claims. (Cl. 75-125) This invention relates to alloy steels capable ofdeep hardening in large sections and more particularly to an alloy steelwhich to an enhanced degree embodies the capability of being readilydeep hardened in large sections and which has improved impactproperties.

There has long been a demand for alloy steels which in addition to beingcapable of deep hardening in large sections are also tough at roomtemperature. Alloys hitherto in use as tool and die steels have beendeficient in one or the other of these properties. Such alloys havingdesirable impact properties are not capable of being deep hardened.Those having desirable deep hardening properties have poor impactproperties.

By deep hardenability I refer to steels which are capable of being oilor air hardened throughout in sections as large as four inches indiameter by four inches long or larger. It has been generallycharacteristic of alloy steels that with an increase of the alloycontent to improve the hardenability capability there has been adecrease in their toughness. Furthermore, even at relatively low carbonlevels, it has been necessary to temper tool and die steels before theyattain their limited impact strength. The alloy set forth in US. PatentNo. 2,355,224 i illustrative of a composition which has an outstandingdegree of deep hardenability but has relatively poor impact strength.

As a practical matter, it is desirable for such steels to be susceptibleto heat treatment at as low a temperature as possible from which theyare cooled in oil or air to provide deep hardenability. Thus, if a steelcan be deep hardened in large sections from hardening temperatures at orbelow 1650 F. their use is greatly facilitated. It is also desirable,for the purpose of facilitating use of the composition in the field asWell as elsewhere, for such steels to have a broad austenitizingtemperature range, i.e., the steel should deep harden upon cooling fromany temperature within a rather broad range. This is particularlyadvantageous in that it is then not necessary to utilize equipment whichis specially adapted to maintain the temperature of the work within acritical and narrow temperature range. Thus, if a steel can be deephardened from only such a narrow austenitizing temperature range of 100F. or less it is far more difiicult for fabricators to produce uniformresults in making their products than if the austenitizing temperaturerange is a band of 150 F. or 300 F. This is especially the case when thecomposition does not require tempering to attain its optimum toughness.

Toughness, as measured by the notched bar impact test, is a verydesirable property in steels capable of deep hardening but it ischaracteristic thereof that such steels require tempering beforeachieving their optimum impact strength. It is an important feature ofmy invention that when my alloy has a carbon content of about 0.45 orless tempering is not required to bring it to optimum toughness. Whenthe carbon content is inire tates Patent F creased and is above about0.45% tempering may be reif i 2,950,968 1C6 Patented Aug. 30, 1960quired to avoid excessive brittleness due to the hardening treatment.

Another very desirable property of alloy steels of this character isthat they have good toughness at low temperatures because of the manyapplications in which such steels are necessarily exposed to lowtemperatures. In the past, it has been considered practically essentialto include a substantial amount of nickel if a hardened steel is not tolose what toughness it has at room tem perature when the temperature islowered. Another important feature of my invention is that when my alloyhas a carbon content not greater than about 0.45% it has good sub-zero,F. or lower, impact properties and is not subject to the well knowntransition temperature effect. This as Well as other unique propertiesare achieved in my compositions Without more than the residual amountsof nickel that are obtained as impurities in melting alloy steels. Suchamounts are usually only a few hundredths of 1%, usually less than about0.2%.

It is an object of this invention to provide an alloy steel which iscapable of deep hardening from a broad austenitizing range oftemperature; which is capable of deep hardening from temperatures belowabout 1650 F and which has good toughness, as indicated by the notchedbar impact test, in the as-quenched or the as quenched and temperedcondition. Another object is to provide such an alloy steel whichretains a considerable proportion of its toughness at temperatures downto l00 F. or even lower. I have found that in order to achieve theunique combination of all of these prop erties, it is necessary toprepare an alloy steel in which the following alloying elements arepresent within the rather narrow ranges as indicated:

Percent Carbon 0.20.8 Manganese 0.5-2.5 Chromium 0.51 .5 Molybdenum0.251.5 Copper 0.65-4

and in which the relative amounts of carbon, manganese and copper arecarefully controlled. As will be more fully pointed out hereinafter,when manganese is present in an amount of only about 0.5% then minimumamounts of about 2% copper and about 0.45 carbon are required to providean alloy having all of the foregoing properties. The remainder of mycomposition is substantially iron which is intended to include suchimpurities as is consistent with good commercial practice as well assuch additional elements which may be in keeping with good metallurgicalpractice but do not impair the aforementioned desirable properties of mycomposition. For example, from the standpoint of good melting practice,I include various amounts of silicon up to about 1%, while such elementsas phosphorus and sulphur are preferably present only in residualamounts. Though vanadium does not appear to have any effect on theimpact properties or hardenability of my composition, I may include upto about 0.5 when its effect in providing grain refinement is desired.

In the accompanying drawings, Figures 1 and 2 are graphs showingrelationships between the alloying elements, carbon, copper andmanganese.

Alloys of this composition can be hardened throughout, in air or oil, insections, four inches in diameter and four inches long or larger to aRockwell C hardness of around 40 to 65, after heating to a temperaturewithin a range of 1500 F. to 1650" F. when the carbon content rangesfrom about 0.5% to about 0.8% while with lower carbon content thetreating temperature range is even broader, being from 1500? F. to 1800F. Such alloys also exhibit excellent toughness, as indicated by notchedbar impact tests. tent of up to about 0.45% such excellent toughness isexhibited even in the as-quenched condition and, while thesecompositions, like other alloy steels, gradually become less tough asthe temperature is lowered, from room temperature to sub-zerotemperatures, they exhibit no sharp decrease in toughness as they arecooled to extremely low temperatures but retain a considerableproportion of their room temperature toughness even when used at the lowtemperatures that exist in arctic climates.

While my composition may deep-harden with as low a carbon content as0.1% it should contain at least 0.2% carbon in order to provide asatisfactory ashardened hardness bearing in mind that the attainableheat treated hardness decreases as carbon is reduced With a carbonconalthough the impact strength improves. Too much carbon detracts fromthe air-hardenability, probably due to the formation of'a-lloy carbides.The upper limit for carbon, therefore, is about 0.8% althoughlower-amounts of carbon are preferable for numerous uses to which thealloy may be put. Articles such as chisels, for example, should containcarbon in the lower portion of the range given, while articles such ashardened steel dies may be made from alloys containing carbon in theupper portion of the range.

Chromium is present primarily to provide oxidation resistance and toreduce scale formation during hot work ing which occurs heavily belowabout 0.5%. Too much chromium adversely affects the low temperatureimpact properties. For this reason it is not desirable to employ morethan about 1.5% chromium. Molybdenum, as well as chromium, is normallyconsidered useful as contributing to the hardenability of alloy steels.However, I have found that molybdenum does not contribute tohardenability to the degree which would be normally anticipated andmainly affects the impact properties of my alloy. For the purpose ofobtaining enhanced irnpact properties I preferably use up to about 1%molyb denum although somewhat more, up to about 1.5%, may be tolerablewith the lower carbon contents of up to about 0.4%. Below about 0.25%,molybdenum is not present in suflicieut quantity to provide the desiredeifect while above about 1.5% molybdenum has an undesirable eifect onthe impact properties of my composition. When chromium and/or molybdenumare utilized in amounts effective to provide deep hardenability, above1.5%, the hardening temperature as well as the impact properties areadversely affected to a marked degree.

Copper and manganese afiect both the hardenability and the impactproperties of my compositions. As will be more fully pointed outhereinafter the carbon content largely controls the amounts of copperand manganese required to provide the minimum deep hardenability in suchlarge sections although for the lower chromium and molybdenum contents Imay use somewhat more copper and manganese. The copper and manganesealso affect the temperature from which the alloys of the presentinvention can be fully hardened in minimum sections of four inches indiameter by four inches long. The addition of copper makes it possibleto maintain a low hardening temperature of 1650 F. maximum. However, atabout 0.5% manganese at least about 2% copper is required to maintainthe low hardening temperature while below those quantities the manganeseand copper are not present in suihcient amounts to provide the desiredrelatively low hardening temperature. From Figure 1 it is apparent thatwith about 0.5 manganese, a minimum of about 2% copper is required toprovide the minimum air harden-ability. required to attain Rockwell(3-59 in a four inch diameter by four inch long section with a carboncontent of about 0.6%. Manganese has a greater efiect than copper onhardenability and at the lower carbon levels I utilize 4 closer tomaximum amounts of manganese to attain the required hardenability. Wherequenching in oil may be utilized the smaller amounts of manganese andcopper are satisfactory.

The curve of Figure l is based upon data obtained from specimens of mycomposition having a carbon content of about 0.6% and with a chromiumand molybdenum content each of about 1%. Compositions falling under thecurve do no contain enough manganese and copper for sufficient airhardenability to attain a minimum hardness of Rockwell C59 in a minimumfour inch by four inch section. The specimens were formed from ingotswhich were processed by forging and rolling and were heated at atemperature of 1600 F. for about 10 minutes and then air quenched. Theweight percent of manganese is plotted along the horizontal scale whilethe weight percent of copper is plotted along the vertical scale. Thepoint on the curve corresponding to 2% manganese, nil copper identifiesthe composition hereinbefore referred to in connection with Patent No.2,355,224 which has relatively poor impact properties.

I have found that a unique improvement in impact properties both at roomtemperature and at extremely low temperatures is obtained in accordancewith my invention by carefully utilizing copper and manganese in amountswhich depend upon the carbon content-of the composition. Therelationship between the three elements, carbon, copper and manganese,is such that in my preferred composition, in addition to the criteria'hereinabove set forth, the value of the ratio of the copper content tothe combined copper and manganese content must be maintained betweencritical limits which must be raised as the carbon content is increasedfrom 0.2%. In Figure 2, lines A and B are plotted to show the minimumand maximum values respectively of the value of this ratio defined asthe percent by weight of copper of the total or combined percent byWeight of the manganese and copper content of the composition. Thecurves of Figure 2 are based on data obtained from tests conducted onspecimens having the composition of the examples enumerated in Table Iand also on specimens having compositions as shown in Table II. Forthese tests specimens /2 inch by /2 inch by 2 /2 inches long wereprocessed and tested in accordance with the standard established by theAmerican Society for Testing Materials. As shown by such standardnotched bar impact tests, alloys of my composition for which the percentof copper of the combined coppermanganese content falls between lines A,B in Figure 2 all show a minimum improvement in toughness of at least50% as compared to deep hardenable alloy steels hitherto known to me.Further, below about 0.45% carbon my composition does not requiretempering but demonstrates exceptional impact strength in its asquenched condition.

At any carbon level, plotted along the vertical scale in Figure 2, linesA, B define along the horizontal scale the values in percent of theratio of the percent-copper content to the combined percent content ofmanganese and copper to provide the improved impact properties of thisinvention but without regard to the aforementioned desirablehardenability or the low treating temperature. Thus with 0.30% carbonthe copper content should form at least 20% of the total manganese andcopper content but no more than 62%. With 0.6% carbon the copper contentshould form at least 61%. At and above 0.6% carbon, manganese is notrequired to provide the improved impact properties and is included, atleast about 0.5%, to provide a minimum as-hardened hardness of RockwellC-59, and the low treating temperature. When copper is present inamounts above about 4% such undesirable metaliurgical phenomena asprecipitation of copper are likely to occur when the alloy is hardenedand drawn. As the manganese content is increased above 2.5% thecomposition becomes difficult to anneal commercially. To achieve aminimum hardness of Rockwell C-59 throughout with air quenching in afour inch round with 0.5% manganese and 0.6% carbon a minimum of 2%copper is required (Figure 1). In order to extend the hardenability toeven larger sections at this carbon and hardness level I may include upto about 4% copper. As shown in Figure 2 such an alloy is characterizedby the improved impact properties of my invention.

' Table I Example No. 0 Mn Cr M0 011 Hardenability 29 l. 52 75 60 1. 80Air Hardening. 31 1. 60 88 67 1. 30 D0. .31 1.92 .81 61 1. 25 Do. 34 1.33 70 1. 42 Do. 39 1. 04 1. 06 62 68 Oil Hardening. .39 .49 .74 .69 .89D0. 41 .92 1.02 30 .68 D0. 42 .91 1.06 .30 1.31 D0. .41 1. 59 1.07 30 1.25 Air Hardening. 47 1. 55 85 67 1. 33 D0. 62 11 1. 00 1. 02 1. 00 OilHardening. .61 .11 1.00 1.02 1.98 Do. 60 l1 1. 00 1. 02 2. 89 AirHardening. 64 51 1. 08 1. 04 1. 04 Oil Hardening. 64 51 l. 08 1. 04 2.00 Air Hardening. .64 .51 1.08 1.04 3.00 D0.

The relative amounts of copper and manganese at the difierent carbonlevels of Examples l16 all fall between lines A, B of Figure 2. Thecareful balance of the alloying elements required is demonstrated by theresults from similar tests conducted on specimens having the compositionof the examples enumerated in Table II, the specimens having beenprocessed as was indicated in connection with Table I.

Table 11 Example N 0. 0 Mn Cr M0 011 Hardenability .29 1. 50 .75 G1 2.80 Air Hardening. .29 1. 48 .75 .61 3. 68 Do. .89 1.04 1.06 .63 15 OilHardening. .39 1.04 1.06 .63 .34 D0. 51 l. 72 78 85 1. 54 Air Hardening.60 1.72 .78 .85 1. 54 Do. .64 1.00 1.03 1.06 1.03 D0. .64 1.00 1.031.06 1. 50 Do. .64 1. 00 1.03 1.06 2.03 D0. 65 1. 48 1.03 1. 02 .50 Do..65 1. 48 1.03 1. 02 1.03 Do. .65 1. 48 1.03 1. 02 1.49 Do. .63 1. 961.05 1.08 .51 D0. .62 1.96 1.05 1.08 1.06 D0. .71 1.72 .78 .85 1. 54 D0.

Specimens having the composition of the examples of Table 11 do not showthe unique improvement in tough ness which is characteristic of thoseset forth in Table I and when plotted in Figure 2 fall outside of thearea between lines A and B. However, those compositions containing 0.2%to 0.45% carbon and in which copper constitutes from about to 80% of thecombined manganese and copper content, are characterized by desirparedto the compositions of Table II. Alloy F will be recognized as a basecomposition of the patent hereinabove referred to.

Alloys of my composition are readily hot workable. No difliculty wasencountered in casting melts into ingots and processing them by forgingand rolling to round cornered square bars.

The eifect of manganese and copper on the hardening temperature and/orhardenability is shown by the hardness attained in a minimum section offour inches diameter by four inches long. The results are given in TableIV where for convenience the manganese and copper contents are alsoincluded:

Table IV Hardening Hardening Temper- Temper- Example No. Mn Or ature,attire, 1,600 F., 1,650 F.,

Rockwell C Rockwell O From Table IV it is apparent that as the manganesecontent is reduced and the copper content is increased, the compositionhas the desired relatively low hardening temperature. When in any one ofmy alloys the manganese content is below about 0.50% and the coppercontent is below about 2% then the low hardening temperature is notmaintained.

The effect of excessive chromium on the low temperature imp-actproperties of my composition is apparent from a comparison of the testresults obtained from specimens having the composition of Example 4 butcontaining 0.89% chromium with the results obtained from a similarcomposition containing 2.18% chromium. Keyhole Oharpy impactmeasurements were made on such specimens which had been air hardenedfrom 1650 F. The specimens containing 0.89% chromium had a' hardness ofRockwell C 51/52 and gave measurements of 19-24 ft.-l-bs. at roomtemperature, 20-17 ft.-lbs. at 0 F., and 16-18 ft.-lbs. at 100 P. On theother hand, specimens with 2.18% chromium had a hardness of Rockwell C48 and gave measurements of 19-15 ft.-lbs. at room temperature, 11-12ft.-lbs. at 0 F., and 28 -ft.-lbs. at -100 F. The sharp drop in impactstrength at the higher chromium level illustrates the adverse effect ofexcessive amounts of this element on the toughness of the composition.

Table V shows the improvement in impact properties for impact piecestreated in the center of a six inch diameter by six inch long sectionfrom a temperature of 1600 F. and tempered at 350 F. for one hour.

able and advantageously useful properties. This is also Table V the caseof those compositions having a carbon content of 0.45% to 0.8% and inwhich copper constitutes at Guinery least 40% of the combined manganeseand copper con- Example Mn Cu Hardness ig g tent- RC Average Specimenshaving the following base compositions were fg prepared for purposes ofcomparison.

Table III 1. 00 .10 50 7.5 1.96 1.05 60 10.5 1. 00 1. 50 00 13.5 1. 002. 03 59. 5 10. 5 0 Mn Cr Mo Cu Hardenability 17.0

33 j gif Izod impact tests on specimens of Example 10, containing .47%carbon, air hardened from 1650 F. but not tempered and having a hardnessof Rockwell C-58 resulted in measurements of 17-21 ft.-lbs. Similarlytreated and tested specimens containing 0.31 carbon, 1.54 mangapactproperties of my composition. The specimens were air hardened from 1650F. and again were not tempered. In the following table the results infoot pounds are shown together with the testing temperature and theashardened hardness.

The absence of a transition temperature efiect in my compositions havingup to about 0.45% carbon makes them especially valuable for use inapplications where low and extremely low temperature conditions may beencountered. l.

The terms and expressions which have been employed are used as terms ofdescription-and not of limitation, and there is no intention, in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

I claim:

1. A hardened alloy steel article having good impact strength,comprising about 0.2 to about 0.8% carbon, about 0.5 to about 2.5%manganese, about 0.5 to about 1.5% chromium, about 0.25 to about 1.5molybdenum, about 0.65 to about 4% copper, the remainder beingsubstantially iron, the percent copper of the combined manganese andcopper content ranging from about to 80% as the carbon content rangesfrom about 0.2 to about 0.45% and from about 40% upwards as the carboncontent ranges from about 0.45 to about 0.8%, tempered at a temperaturebelow that at which copper precipitates when the carbon content isgreater than about 0.45%, and substantially all said copper beingretained in solid solution.

2. A deep hardened alloy steel article having good impact strength,comprising about 0.2 to about 0.8% carbon, about 0.5 to about 2.5%manganese, about 0.5 to about 1.5% chromium, about 0.25 to about l.5%

molybdenum, a mini-mum of 0.65 copper with a combined manganese andcopper content of up to about 4%, the percent copper of the combinedmanganese and copper content in relation to the carbon content being asdelineated between the lines A and B in Figure 2 of the drawing, theremainder being substantially iron, tempered at a temperature below thatat which copper precipitates when the carbon content is greater thanabout 0.45%, and said copper being in solid solution.

3. An untempered alloy steel article hardened to a Rockwell C hardnessof at least 40 through sections at least four inches thick having goodtoughness as indicated by impact tests and containing about 0.2 to 0.45%carbon, about 0.5 to 2.5% manganese, about 0.5 to 1.5 chromium, about0.25 to 1.5% molybdenum, a minimum of 0.65 copper with a combinedmanganese and 7 copper content of up to about 4%, thepercent copper ofthe combined manganese and copper content being as delineated betweenthe lines A and B in Figure 2 of the drawing for the correspondingcarbon content, the remainder being substantially iron, said copperbeing in solid solution.

4. An alloy steel article hardened and tempered to a Rockwell C hardnessof at least 59 through sections at least four inches thick, having goodtoughness as indipated by impact tests and containing about 0.45 to 0.8%

carbon, about 0.5 to 2.5% manganese, about 0.5 to 1.5% chromium, about0.25 to 1.5% molybdenum, a minimum of 0.65% copper with a combinedmanganese and copper content of up to about 4%, the percent copper ofthe combined manganese and copper content being as delineated betweenthe lines A and B in Figure 2 of the drawing for the correspondingcarbon content, the remainder being substantially iron, tempered at atemperature below that at which copper precipitates, said copper beingin solid solution.

5. A hardened alloy steel article having good toughness as indicated byimpact tests and containing about 0.2 to 0.45% carbon, about 0.5 to 2.5%manganese, about 0.5 to 1.5% chromium, about 0.25 to 1.5% molybdenum, aminimum of 0.65% copper With a combined manganese and copper contentof'up to about 4% and with the'percent copper of the combined manganeseand copper content ranging from about 20% to the remainder beingsubstantially iron, said copper being retained in solid solution.

6. A hardened alloy steel article having good toughness as indicated byimpact tests and containing about 0.45 to 0.8% carbon, about 0.5 to 2.5%manganese, about 0.5 to 1.5 chromium, about 0.25 to 1.5% molybdenum, aminimum of 0.65 copper with a combined manganese and copper content ofup to about 4%, the percent copper of the combined manganese and coppercontent ranging from about 40 to the remainder being substantially iron,tempered at a temperature below that at which copper precipitates, saidcopper being retained in solid solution.

7. A hardened alloy steel article having good toughness as indicated byimpact tests at room temperature and at temperatures as low as 100 F.while being free of a transition temperature efliect when cooled as lowas 100 B, said article containing at least 0.1% carbon but less than0.45%, about 0.5 to 2.5% manganese, about 0.5 to 1.5% chromium, about0.25 to 1.5 molybdenum,

a minimum of 0.65% copper with a combined manganese and copper contentof up to about 4%, the percent copper of the combined manganese andcopper content being as delineated between the lines A and B in Figure 2of the drawing for the corresponding carbon content, the re mainderbeing substantially iron, and said copper being retained in solidsolution.

8. A deep hardened alloy steel article having good impact strength andhardened and tempered to a Rockwell C hardness of at least 59 throughsections at least four inches thick, said article containing about 0.6to about 0.8% carbon, about 0.5 to about 2.5% manganese, about 0.5 toabout 1.5 chromium, about 0.25 to about 1% molybdenum, a minimum of0.65% copper with a combined manganese and copper content of up to about4%, the proportions of copper and manganese falling on or above thecurve on the graph in Figure 1, the percent copper of the combinedmanganese and copper content being as delineated between the lines A andB in Figure 2 of the drawing for the corresponding carbon content, theremainder being substantially iron, tempered at a temperature below thatat which copper precipitates, and said copper being retained in solidsolution.

References Cited in the file of this patent UNITED STATES PATENTSSteels, 1950, page 48. Published by McGraw-Hill Book Co., Inc., NewYork, N.Y.

Electric Steel and Alloy Castings, brochurepublished by the SwedishCrucible Steel Co., Detroit, Mich.

Date of first distribution was February 27, 1956.

1. A HARDENED ALLOY STEEL ARTICLE HAVING GOOD IMPACT STRENGTH,COMPRISING ABOUT 0.2 TO ABOUT 0.8% CARBON, ABOUT 0.5 TO ABOUT 2.5%MANGANESE, ABOUT 0.5 TO ABOUT 1.5% CHROMIUM, ABOUT 0.25 TO ABOUT 1.5%MOLYBDENUM, ABOUT 0.65 TO ABOUT 4% COPPER, THE REMAINDER BEINGSUBSTANTIALLY IRON, THE PERCENT COPPER OF THE COMBINED MANGANESE ANDCOPPER CONTENT RANGING FROM ABOUT 20% TO 80% AS THE CARBON CONTENTRANGES FROM ABOUT 0.2 TO ABOUT 0.45% AND FROM ABOUT 40% UPWARDS AS THECARBON CONTENT RANGES FROM ABOUT 0.45 TO ABOUT 0.8%, TEMPERED AT ATEMPERATURE BELOW THAT AT WHICH COPPER PRECIPITATES WHEN THE CARBONCONTENT IS GREATER THAN ABOUT 0.45%, AND SUBSTANTIALLY ALL SAID COPPERBEING RETAINED IN SOLID SOLUTION.